I have tried to clean my grow rocks using a diluted bleach water solution and brushed them around with a big brush.  There is still a white lime looking residue on some of them that doesn’t seem to come off.  Just wondering if you know a good way to clean this off using stuff found around the house?

The grow rocks are dry and need to be soaked in solutions with specific oils to rehydrate.  A product called SM90 from Nutrilife works really well for this.